When a hardwood tree (e.g., red or white oak, ash, maple, poplar) is initially cut down, it has a moisture content ranging from about 60 to about 100%, while a softwood tree (e.g., yellow pine) can have a moisture content as high as 150%. The lumber industry requires that the moisture content of such “green” lumber be reduced to levels of from about 6 to about 8% (via air drying and/or kiln drying) prior to the wood being fabricated into various wood products.
The moisture content of wood, which is usually expressed as a percentage, is the ratio of the amount of water in a piece of wood compared to the weight of that same piece of wood when all of the moisture has been removed. One method for determining the moisture content of wood involves weighing a given sample of wood and recording the weight (the “wet weight”), placing the wood sample in an oven, heating the sample to a temperature of greater than or equal to 108° C. until all of the moisture has been removed, and recording the weight of the dried wood sample (the “oven dry weight”). The moisture content of the wood sample is then determined using the following formula:       %    ⁢                   ⁢    moisture    ⁢                   ⁢    content    ⁢                   ⁢          (      MC      )        =                    (                              wet            ⁢                                                   ⁢            weight                    -                      oven            ⁢                                                   ⁢            dry            ⁢                                                   ⁢            weight                          )                    (                  oven          ⁢                                           ⁢          dry          ⁢                                           ⁢          weight                )              ×    100  
Prior to air and/or kiln drying, green lumber is susceptible to degradation from molds and sapstaining fungi. Molds grow on the surface of wood and cause discoloration through the mass production of spores. Sapstaining fungi penetrate deeply into sapwood (i.e., the central portion or heartwood of the tree) through their dark pigmented threadlike filaments or hyphae and stain wood to a black, blueish or grey appearance. Where lumber customers place a high value on the appearance and quality of the product they receive, wood stain can significantly reduce the value of the lumber by lowering its grade, rendering it less desirable for use in certain applications.
Superficial treatment of freshly cut green lumber is carried out at some mills within twenty-four hours to control staining. Treatments typically take the form of a chemical dip or spray, with known chemical treatments including detergent/bleach/water mixtures, copper-8-quinolinolate, other chemical treatments with a borate base, chlorothalonil (CTL) (tetrachloroisophthalonitrile) organic biocide, organic triazole biocides, ammoniacal solutions, zinc oxide and alkaline salts.
Unfortunately, these chemical treatments have been found to be expensive and/or harmful to the environment. In addition, these treatments are limited in terms of the amount of time the green lumber is protected from mold and sapstaining fungi.
It is therefore an object of the present invention to overcome the drawbacks inherent in known green wood chemical treatments.
It is a more particular object to provide a method for protecting wood and wood products from mold and sapstaining fungi, which employs nontoxic mold inhibitors.
It is another object to provide mold and fungi resistant wood and wood products that may be stored unprotected in the outdoors for longer periods of time without surface or sapwood discoloration.
It is a further object to provide mold and fungi resistant wood and wood products that are protected by a method that employs nontoxic mold inhibitors.